I've been flying drones for a living for 25 years now, all over the world, in all types of airspace and up to 13,000ft.
We had ADS-B out capabilities on the large fixed wing drones I used to fly but would only use it when required by the regulator in complex airspace when it was needed for deconfliction.
As per rodgerc's post It is unlikely that you will need ADS-B out unless you are over 400ft or BVLOS in the medium or large category. I can't see them requiring it for sub 25kg drones below 400ft but it will be interesting to see what comes with the Airservices UTM ecosystem they are currently developing.
Now I rarely fly the drones and spend more time instructing and dealing with CASA for approvals